1998 996 C2

[ATM]

Edited by ATM on Friday 27th April 09:57

[edc]

Not too sure about the new rear spoilers

[LordHaveMurci]

ATM said:

The very rare double booted version!

[ATM]

LordHaveMurci said:

ATM said:

The very rare double booted version!

New fangled Air Brake.

[ATM]

Edited by ATM on Friday 27th April 09:57

[ATM]

Edited by ATM on Friday 27th April 09:57

[ATM]

So yesterday I checked the tyre pressures. Fronts were 27 and rear 33. I put the fronts on 29 and the rears on 37. The result is now a much harder back end with some quite hard bangs going over slight undulations. I might drop them down a bit in a few days if the new harder setup annoys. I understand that if the pressure is too low then the tyre will not sit flat against the road but how can I know if I've gone too low?

[Chris Stott]

ATM said:

So yesterday I checked the tyre pressures. Fronts were 27 and rear 33. I put the fronts on 29 and the rears on 37. The result is now a much harder back end with some quite hard bangs going over slight undulations. I might drop them down a bit in a few days if the new harder setup annoys. I understand that if the pressure is too low then the tyre will not sit flat against the road but how can I know if I've gone too low?

27/33 is pretty low - I haven't been that low with mine.

I'm on stock suspension (265 rears), and run c.32f, c.36r (I think book is 36/42), and the ride is decent. At factory pressures, the car really isn't very nice - bounces and crashes over potholes/bumps.

[ATM]

Chris Stott said:

27/33 is pretty low - I haven't been that low with mine.

I'm on stock suspension (265 rears), and run c.32f, c.36r (I think book is 36/42), and the ride is decent. At factory pressures, the car really isn't very nice - bounces and crashes over potholes/bumps.

I think the standard pressures are madness. I cant understand why anyone would use those unless maybe if they were planning some high speed autobahn runs.

[ATM]

ATM said:

Chris Stott said:

27/33 is pretty low - I haven't been that low with mine.

I'm on stock suspension (265 rears), and run c.32f, c.36r (I think book is 36/42), and the ride is decent. At factory pressures, the car really isn't very nice - bounces and crashes over potholes/bumps.

I think the standard pressures are madness. I cant understand why anyone would use those unless maybe if they were planning some high speed autobahn runs.

I'm still thinking about tyre pressures - perhaps obsessing a little. From a physics perspective surely tyre pressures are related to the weight on the tyre. So trucks which carry large loads run very high pressures. Therefore I'd expect tyre pressures to be very closely related to the weight of the car AND maybe a bit extra for down force and / or cornering forces. All of these will vary a little but you get my point. Now let's compare the 986 Boxster and 996 carrera. I would argue that these cars are very similar. They are the same car from the mid point to the front. The rears are different and I've recently learnt - thanks to c moose - that the wheelbase is longer on the Boxster. As we all know the 996 is heavier at the back but the fronts are basically identical. They were also available with the same size tyres in 17 and 18 sizes. The same n rated tyres too so if you buy into the myths about porsche approved tyres then this means the exact same tyres were approved by porsche for both models. So that's the similarities which I think are considerable. Then we look at the pressures recommended by porsche themselves. I believe the 986 is 28 / 36 and 996 is 36 / 42. So what's going on?

[edc]

For a 986 it's 29f 36r on 18s.

[ATM]

Edited by ATM on Friday 27th April 09:57

[bgunn]

Worth noting, I saw that the GT3 has different tyre pressures again, showing 2.2 bar (31) front and 2.5 bar (36) rear. Or at least that's what I see in the Porsche service manual in the running gear section. Can someone corroborate with an owners manual?

That'll be using sport design wheels as are on my motor, too. Granted, the wheel rate is a lot higher on the GT3 suspension, but it's food for thought.

[ATM]

bgunn said:

Worth noting, I saw that the GT3 has different tyre pressures again, showing 2.2 bar (31) front and 2.5 bar (36) rear. Or at least that's what I see in the Porsche service manual in the running gear section. Can someone corroborate with an owners manual?

That'll be using sport design wheels as are on my motor, too. Granted, the wheel rate is a lot higher on the GT3 suspension, but it's food for thought.

I'm not sure if wheel strength should be a variable worth considering. The only variables I can think of for any given car is the weight on the wheel and the strength of the tyre. Both carcass as in the main tread area and the sidewall. I can guess that a wider tyre needs more pressure because otherwise it would deform but then again I'd guess that a wider tyre would be stiffer in its carcass to prevent this. So given say a 265 tyre and say a 285 tyre on the same car I can see an argument for more pressure on the wider tyre. But otherwise why such a difference?

Then we get into the realms of feel and perhaps a manufacturer such as Porsche can recommend a pressure but if this was to carry a caveat that it achieves the feel that Porsche thinks is wanted then that might make more sense. Given that n rated tyres are approved for various manufacturers I can't imagine how all of them would feel optimum with the same pressure. On the 981 Porsche recommend a pressure and then another for 'comfort'. They do state that on the comfort setting one should not drive over 125. Who the F is doing 125 regularly in this country?

[ATM]

Break down

I noticed a red exclamation mark lit up on the dash yesterday or possibly the day before. Then I noticed the clutch pedal not returning to it's upright position after I had depressed it, only occasionally. I thought ok I'll need to get that checked but did nothing other than pull the clutch pedal back up with my toes and carry on. Fast forward an hour or two of fun driving and I find myself doing some low speed manoeuvres which required the clutch to be pressed for a while and suddenly it does not want to return at all, even if I try to pull it up with my toes. The upshot being I can't really disengage drive and the clutch is basically useless. I looked at the brake fluid reservoir and yes it was low. I walked to a garage and bought some more fluid but it made no difference. I'd guess that it needs bleeding but I can't do that at the side of the road. So i cant drive the car. It feels like a minor break down but still it is a break down.

[Speed addicted]

You topped up the brake fluid because the clutch wasn't working?

[bgunn]

Speed addicted said:

You topped up the brake fluid because the clutch wasn't working?

Errr yes, before you get all mister clever arse. The clutch master cylinder and brakes are fed from a common reservoir on the 996.

[bgunn]

ATM said:

Break down

I noticed a red exclamation mark lit up on the dash yesterday or possibly the day before. Then I noticed the clutch pedal not returning to it's upright position after I had depressed it, only occasionally. I thought ok I'll need to get that checked but did nothing other than pull the clutch pedal back up with my toes and carry on. Fast forward an hour or two of fun driving and I find myself doing some low speed manoeuvres which required the clutch to be pressed for a while and suddenly it does not want to return at all, even if I try to pull it up with my toes. The upshot being I can't really disengage drive and the clutch is basically useless. I looked at the brake fluid reservoir and yes it was low. I walked to a garage and bought some more fluid but it made no difference. I'd guess that it needs bleeding but I can't do that at the side of the road. So i cant drive the car. It feels like a minor break down but still it is a break down.

Look up behind the clutch pedal/is the carpet wet? If so, master cylinder.

Look up on the near side of the gearbox near the top of the bell housing - any signs of wetness? Slave cylinder.

I'll bet the slave seals have gone - bit of a bugger, but it happens.

[Speed addicted]

bgunn said:

Speed addicted said:

You topped up the brake fluid because the clutch wasn't working?

Errr yes, before you get all mister clever arse. The clutch master cylinder and brakes are fed from a common reservoir on the 996.

Hey it was a simple question, I've owned 19 cars over the last 23 years and none of them had a common reservoir!
So to someone without intimate 996 knowledge it seems a bit of a strange thing to be doing.

[LP670]

Speed addicted said:

bgunn said:

Speed addicted said:

You topped up the brake fluid because the clutch wasn't working?

Errr yes, before you get all mister clever arse. The clutch master cylinder and brakes are fed from a common reservoir on the 996.

Hey it was a simple question, I've owned 19 cars over the last 23 years and none of them had a common reservoir!
So to someone without intimate 996 knowledge it seems a bit of a strange thing to be doing.

It would seem to be a german design quirk, had an audi that was the same. non of the british, jap or french cars ive owned have done it that way though.